A bit more detail. In common with many other Cat track loader models (e.g. 955 & 977 which changed from K to L) the 941 model was updated without the Serial Number prefix changing.
Again in common with the larger machines the model update happened in two stages. Then first stage involved machine systems/hardware then later the engine changed from a D300-series of one flavour or another to a 3300-series engine.
In the case of the 941 you can see from the illustration below.
The 941 Serial Number range was machines 80H1-3039.
The 941B was introduced from 80H3040, but retained the same D330 engine as had been fitted to tractors 1-3039 up to machine 80H3883.
From 80H3884-Up the 941B received the 3304 engine.